1. Technical Field
The present invention relates to an interconnect, and more particularly, to an electrically conductive stretchable interconnect capable of maintaining electrical properties even when the interconnect is repeatedly stretched and a method of manufacturing the same.
2. Description of the Related Art
Electronic circuits having excellent flexibility and stretchability are needed to implement a wearable apparatus that may be attached to a human body or an apparatus that may be used as a skin of a robot. An electronic apparatus of which the shape is changed to meet motions such as twisting the human body and bending, unfolding, and extending an arm of the robot may be developed by using the electronic circuits having excellent flexibility and stretchability. As a result, various researches for implementing electronic circuits having flexibility and stretchability have been conducted worldwide.
According to the existing researches known up to now, a stretchable and restorable interconnect connecting between the electronic circuits has been mostly implemented by two methods.
One method forms the interconnect by forming metal conductors having excellent electric conductivity as a two-dimensional or three-dimensional stretchable structure and then burying at least one of the metal conductors into a stretchable and restorable elastic body. The two-dimensional or three-dimensional stretchable structure has bent shapes such as a horseshoe shape, a zigzag shape, a helical shape, and a wave shape. When a bending radius of the stretchable structure is increased, a tensile length is increased but a disposition area of a circuit line is increased to make it difficult to dispose several lines. When the bending radius having the stretchable structure is decreased, a stress applied to a conductor is increased and thus the conductor may be easily fractured upon the repeated tension. Therefore, a conductor having excellent mechanical properties needs to be used.
The other method uses a conductive elastic material. The conductive elastic material having electric conductivity may be formed by fusing nano composites such as CNT and graphene with the elastic material. The conductive elastic material has elasticity but very low electric conductivity. As a result, the elastic conductor is hard to be actually used as the interconnect of the electronic circuits.
Another material used as a conductor in a flexible electronic field is a conductive fiber. Generally, the fiber has various advantages such as diversity of a processing method of drawing (twist), weaving, etc., porosity and wide surface area of the fiber, diversity of surface treatment, and easiness of a composite material composition. In addition to the above advantages, the conductive fiber having electrical properties has been used as an important material even in various electrical and electronic fields. The conductive fiber has been utilized in a textile solar cell, a stretchable transistor, a stretchable display, external stimulus type drug delivery, a biosensor and a gas sensor, light control functional textile, functional clothes, functional products for defense industry, and so on.
The conductive fiber may be processed by various methods in accordance with the use purpose. A representative example may include a conductive twisted yarn formed by twisting the conductive fiber, a conductive sheet formed by weaving or spinning the conductive fiber, a conductive ribbon formed by knitting the conductive twisted yarn, and a conductive tape to which conductive epoxy is added.
Among those, the conductive twisted yarn (or conductive yarn) is mostly used as the interconnect. There are largely two kinds of conductive twisted yarns.
There is a conductive filament yarn formed by braiding the existing metal wires such as copper (Cu) and stainless steel with the existing fiber. The conductive filament yarn uses the existing metal conductor and therefore has excellent electric conductivity but poor durability.
There is a conductive coating yarn formed by coating the existing fibers such as nylon and polyester with conductive materials such as nickel (Ni) and silver (Ag). The conductive coating yarn is formed by coating a surface of fiber like nylon 66 having excellent mechanical properties such as tensile strength, tensile modulus, elongation, bending modulus, and torsional strength with conductive compounds like silver having excellent electric conductivity. Therefore, the conductive coating yarn has electric conductivity lower than that of the metal conductor but very excellent durability.